Enhanced electro-oxidation of formic acid at manganese oxide single crystalline nanorod-modified Pt electrodes

The electrocatalytic activity of Pt towards the oxidation of formic acid is significantly enhanced upon the electrode position of manganese oxide nanorods (in the (11 (1) over bar) single crystalline phase, gamma-MnOOH). The modified Pt electrodes are shown to support the direct oxidation of formic acid to CO2 (i.e., dehydrogenation pathway), while suppressing the dehydration pathway (producing the poisoning intermediate CO). This behaviour is clearly indicated by comparing the intensity of the corresponding two oxidation peaks (I-p(d) and I-p(ind)) observed, respectively, at 0.2 and 0.55 V vs. SCE, where I-d(p) is the peak current of direct formic acid oxidation and I(p)(in)d is the current due to the dehydration (i.e., indirect) pathway of formic acid oxidation. I-p(d) increases with surface coverage theta of MnOOH reaching the highest activity at theta approximate to 30%. MnOOH is believed to play a crucial role as a catalytic mediator which facilitates the charge transfer during the direct oxidation of formic acid into CO2. (C) 2009 Elsevier B.V. All rights reserved